Electrical circuit breaker location devices aid the electrician in identifying a particular circuit interrupting device which is associated with a circuit on which work must be performed. In large installations such as factories and warehouses, it is simply not practical for an electrician to position himself at a circuit breaker panel, de-energize the circuits one by one, thereby disputing the power, and observe which circuit is affected. Furthermore, this practice is unsafe.
In one locator device known in the art, a transmitter unit is simply plugged in to an electrical receptacle in the circuit to be identified. In this transmitter, a diode is connected in series with an RC (resistor-capacitor) circuit and a two-terminal power switch of the thyristor type.
When the circuit is connected across the AC line, the thyristor immediately reaches its trigger voltage (the uncharged capacitor looks like a short-circuit to the line voltage) and a high amplitude spike of current is drawn from the AC line. The spike is short-lived, however, as the capacitor charges to the peak line voltage value. The repetition rate of the current spike can be controlled by the time constant of the RC network. A simple detector is provided for use at the breaker panel to detect the presence of a magnetic field caused by the current spikes propagating down the line.
Unfortunately, generator circuits of the type just described create large magnetic fields that are quite easily coupled to adjacent circuits, thus making positive identification difficult. In addition, the simple receivers employed with systems of this type are subject to false detections because of noise.
Accordingly, a need arises for an electrical circuit locator that is relatively immune to noise, and will only act to detect an identification signal provided by its own associated transmitter. The locator system should be economical and durable, and provide other functions useful to the tradesman, such as a ground fault condition indicator test circuit, electrical receptacle wiring configuration analysis, and simple detection of the presence of AC wiring within walls or other structures.